TEP 0121 - Refine Retries

[XinruZhang]

Create this issue to track the implementation of TaskRun Retries:

• TEP-0121: Task-level Timeout is for each retry attempt for both TaskRun and CustomRun. #5753
• TEP-0121: Implement Retries in TaskRun reconciler #5755
  • Pipeline Controller uses Condition.Succeeded to determine the termination of a TaskRun
• Pipeline controller stop relying on retriesStatus for Custom Task #5810

[XinruZhang]

The only two open sub-issues left:

• TEP-0121: Example code for v1beta1.CustomRun #5754 (will be closed by Add a PipelineRun Example for Creating a Wait CustomRun #5906)
• Cleanup isRunRetriable in the release v0.47.0 #5870

Those are all cleanups, which won't block marking TEP-0121 as implemented (tektoncd/community#905).